The present invention relates to a reusable type end mill used for performing a grooving or fluting operation on various types of workpieces.
A prior art reusable end mill of the concerned type is disclosed by way of example in Japanese Utility Model Publication No. 6-7855. The end mill disclosed in this publication is constructed as follows. A plurality of tip mounting seats are spirally arranged on the outer periphery of a generally cylindrical end mill body. Quadrilateral tabular replaceable tips (hereinafter referred to as "the tips") whose each surface forming the quadrilateral shape is used as an outer peripheral relief face, are detachably mounted on the respective tip mounting seats in such a manner that the tips are directed toward the outer periphery of the end mill. Edges formed on the tips constitute the outer peripheral edges of the end mill and are arranged such that no gap is formed between the rotation loci of the edges formed on the tips around the axis of the end mill body.
On the other hand, a quadrilateral tabular tip is known which is formed in a shape different from the tips having the above-described outer peripheral edges. Such tip is attached to the outer periphery of the forward end of the end mill body in such a manner that the face of the tip forming the quadrilateral shape is directed toward the forward end of the end mill. One of the edges formed on side ridges of the face forming the quadrilateral shape is used as an end cutting edge of the end mill. A forward-end and outer-peripheral edge is further provided on the tip, as well as the end cutting edge, in such a way that the forward-end and outer-peripheral edge extends from the end cutting edge and is directed toward the outer periphery of the forward end of the end mill body. No gap is formed between the rotation locus of the outer peripheral edges around the rotation axis O and the rotation locus of the rear end of the forward-end and outer-peripheral edge so that the forward-end and outer-peripheral edge can constitute the forward end portion of the outer peripheral edges.
However, the reusable type end mill constructed as described above presents the following problems. The tip forming the end cutting edge differs in shape from the tips forming the outer peripheral edges, which inevitably makes the maintenance of tips in an end mill body complicated and troublesome. In particular, the tip attached to the forward end of the mill body constitutes not only the end cutting edge, but also the forward-end and outer-peripheral edge which singly forms the forward end portion of the outer peripheral edges. Accordingly, this type of tip becomes worn very quickly. In addition to this disadvantage, since this tip is formed in a shape different from the other tips constituting the outer peripheral edges, the two types of tips are not interchangeable. This requires that an extra tip of the former type be kept in hand in advance in order to speedily accommodate the aforementioned rapid wear, with the result that the maintenance of tips becomes more complicated and troublesome.